Liquid resistor apparatus

ABSTRACT

Liquid resistor apparatus in which electrically conductive liquid is transferred from a control chamber to a controlled chamber, thereby affecting the electrical resistance between electrodes in the controlled chamber, as a result of evaporation of liquid in the control chamber by control current passed therethrough, there being a liquid passage and a restricted vapor passage connecting the two chambers. The restriction in the vapor passage is set during operation and may be adjustable to govern the operating characteristics of the apparatus.

United States Patent [72] Inventor Norbert Roger Beyrard Paris, France [21] Appl. No. 808,274

[22] Filed Mar. 18, 1969 [45] Patented Sept. 28, 1971 [731 Assignee Association des Ouvrlers en Instruments De Precision Paris, France a part interest [32] Priority Mar. 27, 1968 [33] France [54] LIQUID RESISTOR APPARATUS [56] References Cited UNITED STATES PATENTS 2,249,738 7/1941 Brownfield 200/50 2,855,545 8/1958 Benchemoul 317/11 Primary ExaminerRodney D. Bennett, Jr. Assistant ExaminerR. Kinberg Attorney-Mauro & Lewis ABSTRACT: Liquid resistor apparatus in which electrically conductive liquid is transferred from a control chamber to a controlled chamber, thereby affecting the electrical resistance between electrodes in the controlled chamber, as a result of evaporation of liquid in the control chamber by control current passed therethrough, there being a liquid passage and a restricted vapor passage connecting the two chambers. The restriction in the vapor passage is set during operation and may be adjustable to govern the operating characteristics of the apparatus.

7 Claims, 7 Drawing Figs.

[52] US. Cl 338/38, 338/80, 338/81, 338/86, 338/94, 338/195, 338/222 [51] Int. Cl ..II01c 11/00 [50] Field of Search 338/27, 36, 38, 80, 81, 86, 94,195, 222

I8 I i PATENTEVUI sms m v sum 2 or 2 LIQUID RESISTOR APPARATUS The invention relates to liquid resistor apparatus and a method of current control using the apparatus.

French Pat. No. 1,492,814 describes liquid resistor apparatus in which current passing through conductive liquid vaporizes the liquid and the escape of vapor is controlled by a pressure-responsive or solenoid-operated valve. The present invention seeks to provide improved liquid resistor apparatus.

According to the invention there is provided liquid resistor apparatus comprising a closed control chamber and a closed controlling chamber, the chambers communicating with each other via a first passage extending between regions at or near the bottoms of the two chambers and a second passage extending between regions at or near the tops of the two chambers; a first pair of electrodes in the control chamber and second pair of electrodes in the controlled chambers, the electrodes passing current through electrically conductive liquid in the chambers, the second passage presenting a restriction to vapor flow, which restriction is set and independent of vapor pressure, the restriction and the bore of the first passage being so related as to ensure that evaporation of liquid in the control chamber displaces liquid therefrom into the controlled chamber.

in a preferred embodiment of the invention the controlled chamber is disposed above the control chamber.

T he invention also provides a method of controlling electric current consisting in taking liquid resistor apparatus as set forth above charged with conductive liquid, passing controlling current between the control electrodes to vaporize liquid in the control chamber so that the vapor escapes at a controlled rate through the set restriction and liquid passes into the controlled chamber, and arranging that the current to be controlled passes between the electrodes in the controlled chamber.

The method may be such that the restriction is set to give an effective bore for the second passage which is very small in relation to the bore of the second passage and the control current is such that the liquid in the control chamber is very rapidly discharged into the second chamber, the apparatus thereby giving a switching characteristic.

Alternatively, the method may be such that the size of the restriction and the magnitude of the control current are such that continuous control of the controlled current is efiected in response to continuous control of the control current.

To enable the controlled current changes to be an amplification of the control current changes, steps may be taken to promote differential additional generation of vapor in the chambers. For this purpose, the surface areas of the electrodes may be increased and, furthermore, the distance between them may be varied.

The generation of vapor in the control chamber can be arranged to be initially great employing electrodes that are closed together at their upper parts and spaced apart at their lower portions. The same result can be achieved by means of bafl'les disposed in the chamber at the lower part. in this way a certain quantity of vapor is rapidly obtained which brings the apparatus to the working condition, after which regulation is carried out by using portions of electrodes that are spaced farther away from each other.

One of the chambers or both of them can be provided with safety means (valves, fusible stoppers, shear devices, etc.) so as to avoid the inconveniences of an excessive rise in pressure in the apparatus.

The invention will further be described with reference to the accompanying drawings, of which:

FIG. 1 is a schematic cross-sectional elevation of apparatus according to the invention.

FIGS. 2 and 3 are sections on lines ll-ll and Ill-Ill respectively of FIG. 1.

FlG. 4 shows an example of a system incorporating such apparatus.

FIGS. 5 and 6 show two variants of the form of the control chamber, in sections similar to those of FIG. 1.

FIG. 7 is a section on line Vll-Vll of FIG. 6.

.The liquid resistor apparatus shown in FIGS. 1 to 3 comprises a container 1 of parallelepiped form and made of insulating material, this container being divided into two chambers 3 and 4 by a partition 2 and being closed by a fluidtight cover 5. The chambers 3 and 4 communicate with each other at their lower parts by way of a pipe 6 which is integral with the partition 2 and, at their upper parts, by way of a pipe 7 which can be restricted to varying degrees by a pointed screw 8 engaged in a tapped hole 9 in the cover 5.

Rectangular electrodes 11 and 12, which face each other, are fitted against the two small sides of the chamber 3 and are connected to external terminals 13 and 14 having pins which pass through the walls of the container 1 for attachment to the electrodes. Fitted against the large sides of the chamber 4 are electrodes 15 and 16 which are narrower at the bottom than at the top, so that the electrode surface that is submerged as the level N of liquid 17 rises increases at a greater rate than the change in said level. The electrodes 15 and 16 are connected respectively to terminals 18 and 19 supported on the cover 5.

The partition 2 and the cover 5 have small orifices 22 and 22a to enable electrolysis gases to escape; also, the cover 5 is provided with a calibrated safety valve 20, whilst the thickness of the partition 2 is locally reduced at 21 so as to yield in the event of the pressure being excessive.

In use, the apparatus functions as follows. initially, the electrically conductive liquid entirely fills the chamber 3 and only a small quantity of liquid is present at the bottom of chamber 4, possibly submerging the base of the electrodes 15 and 16. The electrical resistance between these electrodes is thus high and may even be virtually infinite if no contact is made with the liquid.

A source of control current is connected between the terminals l3 and 14, and current therefrom heats the liquid in the chamber 3, which liquid begins to vaporize. Liquid is driven through the pipe 6 into chamber 4 by the pressure of the vapor which escapes with difficulty through the pipe 7. The level N of the liquid in the chamber 4 having risen, the resistance between the electrodes 15 and 16 diminishes.

Thus, an increase in the density of the current between the electrodes 11 and 12 causes a reduction in the resistance between the electrodes 15 and 16 and, consequently, an increase in controlled current which passes in series between terminals 18 and 19.

In the case of aqueous liquids, it can be estimated that in the neighborhood of the boiling temperature, an energy of 2 joules suffices to produce 1 cubic centimeter of vapor. For the purpose of controlling systems employing considerable power, let us say about 10 kilowatts, the volume of the chambers can be of the order of several tens of cubic centimeters. Thus, with a relatively wide tube 6 and a tube 7 that is almost blocked, the transfer of liquid from the chamber 3 can be readily achieved in a fraction of a second. Conversely, with a tube 6 of small diameter, 2 millimeters for example, and a tube 7 that permits appreciable escape of vapor, the transfer may require several tens of seconds. Thus, an instant response giving a switching characteristic or a delayed response can be achieved, the latter offering special advantages in automatic systems for the purpose of avoiding sudden starts and a pumping effect.

It should be noted that in order to reduce leakage current, it is of advantage to restrict the passages for the liquid between the two chambers, that is to say, to employ a tube 6 that is always relatively narrow.

In the embodiment shown in FIG. 1, the resistance between the terminals 13 and 14 is appreciably greater than between the terminals 18 and 19 due to the difference between the distance separating the electrodes and between their surfaces. This apparatus thus functions as a current amplifier, the control current passing through the chamber 3 and the controlled current through the chamber 4.

It may also be desired to heat the liquid in the control chamber rapidly so as to bring the apparatus to the normal operating condition, subsequent generation of vapor then being reduced. The control chambers illustrated in FIGS. 5, 6 and 7 provide this result.

Referring to FIG. 5, the electrodes 11 and 12 comprise, at the top, portions 23 and 24 that are quite closer together, then, two inclined portions 27 and 28 separated from each other by two horizontal portions 25 and 26. Thus, the farther the level in the chamber 3 drops, the more the resistance between the electrodes increases and the more the voltage at the terminals 13 and 14 must increase to keep pace with the generation of vapor.

A similar result is obtained with the chamber shown in H68. 6 and 7. Fitted between the electrodes 11 and 12 in chamber 3 are relatively tall bafile partitions 31, 32 and 33 and shorter partitions 34 to 39. Thus, when the chamber 3 is full of liquid, the current path between the electrodes 11 and I2 is direct. When the liquid drops below the tops of the partitions 31 to 33, the current path is of reduced section and follows the line 40; when the liquid drops below the tops of the bafiles 34 to 39, the current follows the still more lengthened line 41 and the section through which the current pa ses can be still further reduced.

An arrangement for amplifying current is illustrated in FIG. 4. An electrical load W receives current from power source terminals U through a series resistor R, and a parallel combination of a resistor R and the resistance R of the controlled chamber of the above-described liquid resistor apparatus. A control current source u is connected in series with a rheostat P to the terminals 13 and 14 of the controlled chamber of the apparatus. By adjusting the rheostat, the current in the control chamber can be varied, so varying the quantity of vapor generated, the value of R and thus the current through the load W.

Thus, if load W is an induction motor, it is possible to start up the motor with an auxiliary control current, the rotor of the motor being in series with the resistance R,, between the electrodes l and 16. The control current can be derived in various ways from the main motor current. For example, the terminals l3 and 14 can be connected to the terminals of the electric motor.

The chamber 4, and in particular the cover 5, can be provided with fins or can be cooled to ensure condensation of the vapor passing thereto through the passage 7. Liquid losses, even when the equipment is in continuous service, can thus be considerably reduced. Thus, with an appropriate control current that maintains a vapor-pressure in the chamber 3 such that the liquid is maintained in the chamber 4, it is possible to provide an auxiliary apparatus which, in normal service, short circuits the terminals 18 and 19. Such apparatus can be envisaged in controlling power levels of several kilowatts.

It is to be understood that a particular advantage of the above-described method of use of apparatus arranged as shown in the drawings is that the controlled resistance of the apparatus is initially large and decreases as operation proceeds to a low value.

The above-described apparatus is suitable for alternating current and, if the release of gas due to electrolysis is slight or if the liquid used does not electrolyse (e.g. mercury), the equipment is suitable for use with continuous current.

The invention is not restricted to the details of the abovedescribed embodiment thereof. For example, electrodes may be arranged in star or delta configuration in at least the controlled chamber, permitting the passage of three-phase current, these being fitted in the same chamber. Also, using a single control chamber, itwould be possible to control the level of liquid in three chambers each containing a pair of electrodes also permitting the control of three-phase current.

What I claim is:

1. Liquid resistor apparatus comprising a closed control chamber and a closed controlled chamber, the chambers communicating with each other via a first passage extending between regions at the bottoms of the two chambers and a second passage extending between regions at the tops of the two chambers; a first air of electrodes in the control chamber and a second pair of e ectrodes in the controlled chamber, the

electrodes passing current through electrically conductive liquid in the chambers, the second passage presenting a restriction to vapor flow, which restriction is set and independent of vapor pressure, the restriction and the bore of the first passage being so related as to ensure that evaporation of liquid in the control chamber displaces liquid therefrom into the controlled chamber.

2. Apparatus as claimed in claim 1 wherein the controlled chamber is disposed above the control chamber.

3. Apparatus as claimed in claim 2 wherein the chambers are the upper and lower parts of a container divided by a horizontal partition, the first passage being the bore of a pipe extending from the partition to near the bottom of the control chamber and the second passage being the bore of a pipe extending from the partition to near the top of the controlled chamber.

4. Apparatus as claimed in claim 1 wherein adjustment means are provided to adjust the setting of the restriction.

5. Apparatus as claimed in claim 1 wherein the electrodes in the controlled chamber are opposed, vertically extending electrodes which are wider at the top than at the bottom.

6. Apparatus as claimed in claim 1 wherein the electrodes in the control chamber are closer together at the top than at the bottom.

7. Apparatus as claimed in claim 1 wherein the control chamber is further provided with a set of baffles arranged in such manner to give a longer current path through the liquid between the electrodes when the liquid is at a low level than when it is at a high level. 

1. Liquid resistor apparatus comprising a closed control chamber and a closed controlled chamber, the chambers communicating with each other via a first passage extending between regions at the bottoms of the two chambers and a second passage extending between regions at the tops of the two chambers; a first pair of electrodes in the control chamber and a second pair of electrodes in the controlled chamber, the electrodes passing current through electrically conductive liquid in the chambers, the second passage presenting a restriction to vapor flow, which restriction is set and independent of vapor pressure, the restriction and the bore of the first passage being so related as to ensure that evaporation of liquid in the control chamber displaces liquid therefrom into the controlled chamber.
 2. Apparatus as claimed in claim 1 wherein the controlled chamber is disposed above the control chamber.
 3. Apparatus as claimed in claim 2 wherein the chambers are the upper and lower parts of a container divided by a horizontal partition, the first passage being the bore of a pipe extending from the partition to near the bottom of the control chamber and the second passage being the bore of a pipe extending from the partition to near the top of the controlled chamber.
 4. Apparatus as claimed in claim 1 wherein adjustment means are provided to adjust the setting of the restriction.
 5. Apparatus as claimed in claim 1 wherein the electrodes in the controlled chamber are opposed, vertically extending electrodes which are wider at the top than at the bottom.
 6. Apparatus as claimed in claim 1 wherein the electrodes in the control chamber are closer together at the top than at the bottom.
 7. Apparatus as claimed in claim 1 wherein the control chamber is further provided with a set of baffles arranged in such manner to give a longer current path through the liquid between the electrodes when the liquid is at a low level than when it is at a high level. 